FRIT SALVAGE INNOVATION OF CATHODE-RAY TUBE BY INITIATING TO CRACK ALONG THE SEAL EDGE

This article describes a thermal stress boundary element analysis whic h was carried out to select a mechanical device that would innovate th e frit salvage of cathode ray tubes (CRT). The panel and funnel of a C RT an fritted at the seal edge. To reuse a CRT, the panel and funnel a re separated by etching and then applied a thermal shock. This procedu re is known as frit salvage. Current yield of the frit salvage success rate is about 61%, which means that 39% of the components are lost an d cannot be reused. The financial burden can be reduced if the salvage rate is improved through a better understanding of the thermal shook mechanism. During thermal shock, a crack was observed to initiate at t he end of the axes and traverses towards the corner along the seal end . A CRT is lost when the crack travels along the diagonal corner. A th ermal stress analysis was carried out using the boundary element metho d. The analysis determined that maximum stresses are located near the blend radius on the panel skirt at approximately 1-2 inches on either side of the diagonal. Also it was found that the stresses along the fr it seal edge are uniform from the end of the major and minor axes towa rds the diagonal. The stresses at the diagonal location were reduced b y approximately 29%. The direction and location of the crack obtained by the boundary element anlysis were consistent with those observed in the frit salvage procedure. The crack's promoter along the seal edge is used to protect thermal shock on the outer face panel near the heel radius in order to prevent thermal failure on the diagonal corner. Th e resultant stresses' directions through the crack's promoter have two holds. The directions of the dominant high stresses at the seal edge through the crack's promoter were changed perpendicular to the seal ed ge. Therefore, it induces the crack to follow along the seal edge. Sec ondly, the stresses' directions on a diagonal corner have also been ch anged to be perpendicular to the seal edge. Consequently, this will pr event the crack along the seal edge from propagating to the diagonal c orner, as the crack will advance normally to the maximum principal str ess. The crack continues to traverse along the dominant high stress li nes at the seal edge as required for a successful frit salvage process . This application is an excellent example of the advantages of using the boundary element method in an industrial setting. (C) 1998 Elsevie r Science Ltd. All rights reserved.